A preparation method of red yeast rice pigment and the prepared red yeast rice pigment

Abstract

The present application discloses a method for preparing a red yeast rice pigment and the red yeast rice pigment obtained thereof, and relates to the field of food additives. Wherein, the method for preparing the red yeast rice pigment comprises the following steps: S1, inoculating the monascus species into a basal culture medium to carry out batch expansion cultivation operation; S2, after the colony in step S1 matures, centrifuging and taking the solid residue, adding 3 5 times the volume concentration of 95% or more alcohol, stirring, then solid-liquid separation and taking the liquid, concentrating at 45 ℃ 55 ℃ to obtain a concentrated solution; S3, adding a protective agent to the concentrated solution of step S2, after high-speed stirring is uniform, cooling and solidifying, the protective agent adopts at least one of maltodextrin, gum arabic, and sodium alginate aqueous solution; S4, the product after cooling and solidifying in step S3 is freeze-dried to obtain red yeast rice pigment. The red yeast rice pigment obtained by the above method has the advantages of high yield and high thermal stability.

Description

Technical Field

[0001] The present application relates to the field of food additives, and in particular to a method for preparing red yeast rice pigment and the red yeast rice pigment obtained therefrom. Background Art

[0002] Monascus red is a red food additive fermented from Monascus purpureus. It is a secondary metabolite of Monascus purpureus and possesses rich nutritional and medicinal value. Monascus red pigment is non-toxic and harmless, abundantly available, highly safe, and naturally colored. It also exhibits numerous physiological activities, including antioxidant, anti-tumor, and anti-fatigue properties. It is widely used in coloring meat products, pasta, and alcoholic beverages.

[0003] Currently, the production process of red yeast rice mainly includes the selection and optimization of fermentation medium, biotransformation, physical and chemical extraction, and separation and drying. Among them, spray drying is currently widely used in the drying of red yeast rice pigment due to its rapid drying characteristics. However, spray drying needs to be carried out under high temperature conditions, which can easily cause the inactivation of the active substances in red yeast rice pigment. In addition, red yeast rice pigment is prone to fading when exposed to heat during subsequent storage, which reduces the market competitiveness of red yeast rice pigment. Summary of the Invention

[0004] The present application provides a method for preparing red yeast rice pigment and the red yeast rice pigment prepared therefrom, so as to solve the problems that the existing spray drying method of red yeast rice pigment easily causes loss of active substances and the red yeast rice pigment easily fades when exposed to heat during subsequent storage.

[0005] In the first aspect, the present application provides a method for preparing red yeast rice pigment using the following technical solution:

[0006] A method for preparing red pigment of monascus comprises the following steps:

[0007] S1. Inoculate the Monascus species into the basic culture medium to carry out batch expansion operations;

[0008] S2. After the bacterial colonies in step S1 mature, centrifuge to obtain the solid residue, add 3-5 times the volume of alcohol with a concentration of more than 95%, stir, then separate the solid and liquid to obtain the liquid, and concentrate at 45°C-55°C to obtain a concentrated solution;

[0009] S3. Add a protective agent to the concentrated solution of step S2, stir at high speed until uniform, and cool and solidify, wherein the protective agent is at least one of maltodextrin, gum arabic, and sodium alginate aqueous solution;

[0010] S4. Freeze-dry the product after cooling and solidification in step S3 to obtain red pigment of Monascus koji.

[0011] The difference from the existing method is that: (1) the present invention adopts freeze drying to freeze dry the concentrated liquid obtained after fermentation of Monascus species to obtain Monascus red pigment; freeze drying is carried out at low temperature and low pressure, which can prevent the problem of high temperature degradation of Monascus red pigment; (2) in view of the fact that the molecular structure of macromolecules such as protein and polysaccharide in Monascus red is easily squeezed by ice crystals and molecular chain breaks or spatial structure changes occur when the concentrated liquid is directly freeze dried, forcing the effective components of Monascus red pigment to be damaged by ice crystals. Therefore, the present invention adds a protective agent before freeze drying the concentrated liquid. The protective agent adopts at least one of maltodextrin, gum arabic and sodium alginate aqueous solution. The protective agent can be embedded on the surface of Monascus red pigment to form Monascus red pigment with an embedded structure. Among them, the protective agent can protect the effective components of Monascus red pigment from ice crystal damage on the one hand, thereby improving the yield of Monascus red pigment, and on the other hand, it can also reduce the influence of the external environment on Monascus red pigment, which is conducive to improving the thermal stability of Monascus red pigment.

[0012] Specifically, the present application adds a protective agent to the concentrated solution and then recovers the red yeast rice powder product by freeze drying. The yield of the red yeast rice powder product is as high as more than 98%, while the concentrate is directly freeze dried without adding a protective agent, and the yield of the red yeast rice powder product is 90-95%. In addition, the recovery rate of red yeast rice spray drying is between 50-90%. By optimizing process parameters and adding protective agents, the highest recovery rate of the spray drying method is 85%-90%. That is, when the red yeast rice powder product is recovered by spray drying, it is difficult to achieve a recovery rate of more than 95%. In summary, the method of the present application is used to recover the red yeast rice powder product, which has better recovery stability and higher yield.

[0013] Preferably, the protective agent comprises maltodextrin, gum arabic and a sodium alginate aqueous solution with a mass concentration of 1.5%-2.5%, the amount of maltodextrin is 15%-25% by weight of the concentrated solution in step S2, the amount of gum arabic is 4%-6% by weight of the concentrated solution in step S2, and the amount of the sodium alginate aqueous solution with a mass concentration of 1.5%-2.5% is 0.2%-0.3% by weight of the concentrated solution in step S2.

[0014] In the present application, when maltodextrin, gum arabic and sodium alginate are used as protective agents, the wall material structure on the surface of red yeast rice pigment can be improved under the coordinated cooperation of the three maltodextrin, gum arabic and sodium alginate in a reasonable ratio. The wall material structure can be protected from ice crystal damage and denaturation degradation during the freeze-drying process, and has a uniform and tiny porous structure, which is convenient for the diffusion and sublimation of water vapor while preventing the loss of effective ingredients, thereby improving the drying effect of red yeast rice pigment. In addition, the wall material structure can also reduce the impact of the external environment on the red yeast rice pigment, which is conducive to improving the thermal stability of the red yeast rice pigment.

[0015] Further preferably, the amount of maltodextrin is 20% by weight of the concentrated solution in step S2, the amount of gum arabic is 5% by weight of the concentrated solution in step S2, and the amount of sodium alginate aqueous solution with a mass concentration of 1.5%-2.5% is 0.25% by weight of the concentrated solution in step S2.

[0016] Preferably, the DE value of the maltodextrin is 16-20.

[0017] In this application, the DE value of maltodextrin is preferably 16-20. The maltodextrin molecular chain within this DE value range is shorter, the degree of polymerization is lower, and the solubility and dispersibility are good. It can improve the drying effect and product uniformity of red yeast rice pigment while improving the water solubility and quality stability of red yeast rice pigment.

[0018] Preferably, the molecular weight of the gum arabic is 220,000-300,000.

[0019] In the present application, the molecular weight of gum arabic is preferably 220,000-300,000, wherein gum arabic within this molecular weight range can be evenly dispersed in the concentrate and can serve as a stabilizer during the freezing process of red yeast rice pigment, thereby enhancing the stability of red yeast rice pigment and preventing red yeast rice pigment from denaturing or degrading during the freeze-drying process, which is conducive to obtaining red yeast rice pigment that is both water-soluble and stable.

[0020] Preferably, in the sodium alginate aqueous solution with a mass concentration of 1.5%-2.5%, the molecular weight of the sodium alginate is 50,000-100,000.

[0021] In the present application, the molecular weight of sodium alginate is preferably 50,000-100,000, which is beneficial to improving the drying effect and product uniformity of the red yeast rice pigment and is conducive to obtaining red yeast rice pigment with good water solubility and stable quality.

[0022] In step S3, the rotation speed of the high-speed stirring is 10000 r / min-15000 r / min.

[0023] In the present application, the rotation speed is controlled within the above range. On the one hand, the protective agent can be evenly dispersed in the concentrated liquid, which is beneficial to improving the embedding effect of the finished red yeast rice pigment, thereby improving the stability of the red yeast rice pigment; on the other hand, it can also protect the red yeast rice pigment from shear damage, which is beneficial to improving the yield of the red yeast rice pigment.

[0024] In step S3, the curing temperature is (-38°C) to (-45°C).

[0025] Preferably, in step S4, the freeze-drying comprises the following steps:

[0026] S41. Dehydrate for 1-2 hours in an environment with a temperature of -25°C to -20°C and a vacuum degree of 5Pa-10Pa;

[0027] S42. Dehydrate for 1-2 hours in an environment with a temperature of -15°C to -10°C and a vacuum degree of 5Pa-10Pa;

[0028] S43. Dehydrate in an environment with a temperature of -6°C to 0°C and a vacuum degree of 5Pa to 10Pa for 2-4 hours;

[0029] S44. Dehydrate in an environment with a temperature of 1°C to 5°C and a vacuum degree of 5Pa-10Pa for 2-4 hours;

[0030] S45. Dehydrate in an environment with a temperature of 6°C to 10°C and a vacuum degree of 5Pa-10Pa for 4-6 hours;

[0031] S46. Dehydrate for 1-2 hours in an environment with a temperature of 10°C to 15°C and a vacuum degree of 5Pa-10Pa;

[0032] S47. Dehydrate for 1-2 hours in an environment with a temperature of 20°C to 25°C and a vacuum degree of 5Pa-10Pa;

[0033] S48. Dehydrate for 6-8 hours in an environment with a temperature of 30℃~35℃ and a vacuum degree of 5Pa-10Pa.

[0034] In the present application, the red yeast rice pigment is freeze-dried according to the above freeze-drying curve, which is beneficial to prevent the unevenness in the crystallization and de-crystallization process, thereby improving the uniformity and stability of the red yeast rice product, so as to better retain the active ingredients and original quality of the red yeast rice product, and improve the drying effect of the red yeast rice pigment, and reduce the water content of the red yeast rice pigment. In addition, the design of the above freeze-drying curve of the present application can also reduce energy consumption, reduce production costs, shorten the time of the entire freeze-drying process, and thus improve production efficiency.

[0035] In a second aspect, the present application provides a red yeast rice pigment, which is prepared by any one of the above-mentioned methods for preparing the red yeast rice pigment.

[0036] The red yeast rice pigment of the present application is obtained by freeze-drying, and a protective agent is added during the freeze-drying process. The freeze-drying process is carried out under low temperature and low pressure conditions, so that the water in the red yeast rice pigment is directly sublimated from the solid state to the gas state, avoiding the problems of reduced pigment activity, discoloration, decomposition, etc. caused by high-temperature drying. In addition, the addition of the protective agent protects the effective ingredients of the red yeast rice pigment from damage by ice crystals, retains the color value and other properties of the red yeast rice pigment to the greatest extent, and ensures its quality in application.

[0037] In summary, this application has at least the following beneficial technical effects:

[0038] (1) The present application adds a protective agent to the concentrated solution and then recovers the red yeast rice powder product by freeze drying. The yield of the red yeast rice powder product is as high as more than 98%. The yield of the red yeast rice powder product is 90-95% when the concentrated solution is directly freeze dried without adding a protective agent. In addition, the recovery rate of red yeast rice spray drying is between 50-90%. By optimizing process parameters and adding protective agents, the highest recovery rate of the spray drying method is 85%-90%. That is, when the red yeast rice powder product is recovered by the spray drying method, it is difficult to achieve a recovery rate of more than 95%. In summary, the method of the present application is used to recover the red yeast rice powder product, which has better recovery stability and higher yield. In addition, it can also reduce the impact of the external environment on the red yeast rice pigment and improve the thermal stability of the red yeast rice pigment.

[0039] (2) In the present application, when maltodextrin, gum arabic and sodium alginate are used as protective agents, the wall material structure of the red yeast rice pigment surface can be improved under the synergistic cooperation of the three maltodextrin, gum arabic and sodium alginate in a reasonable ratio. The wall material structure can not only be protected from ice crystal damage and denaturation and degradation during the freeze-drying process, but also has a uniform and tiny porous structure, which facilitates the diffusion and sublimation of water vapor while preventing the loss of effective ingredients, thereby improving the drying effect of the red yeast rice pigment. In addition, the wall material structure can also reduce the impact of the external environment on the red yeast rice pigment, which is beneficial to improving the thermal stability of the red yeast rice pigment. DETAILED DESCRIPTION

[0040] The present application is further described below in conjunction with specific experiments.

[0041] Example

[0042] [Example 1]

[0043] A method for preparing red pigment of monascus comprises the following steps:

[0044] S1. Inoculate the Monascus species into a basal culture medium, control the temperature at 35° C., and culture in a shake flask for 6 days; wherein the Monascus species is a purple Monascus species numbered CGMCC No. 3.15548 purchased from the Institute of Microbiology, Chinese Academy of Sciences, and the basal culture medium comprises 10 g of rice flour, 2 g of corn steep liquor powder, 1 g of glucose, 10 g of peptone, 15 g of sodium nitrate, 0.2 g of magnesium sulfate, and 0.15 g of potassium dihydrogen sulfate, and the pH is adjusted to 7.0 to obtain a culture medium;

[0045] S2. After the bacterial colonies in step S1 mature, the solid residue is centrifuged and separated. 4 times the volume of alcohol with a concentration of 95% or more is added. The mixture is stirred at a stirring speed of 100 r / min for 10 h. The liquid is then separated and concentrated at 50° C. using a low-temperature vacuum concentrator to obtain a concentrated solution. The solid content of the concentrated solution is 38.2%;

[0046] S3. Add a protective agent to the concentrated solution of step S2, stir at a high speed of 10,000 r / min for 5 minutes, and then cool to -38°C for solidification; the protective agent is specifically maltodextrin with a DE value of 16-20, and the amount of maltodextrin is 15% by weight of the concentrated solution of step S2;

[0047] S4. The product solidified by cooling in step S3 is freeze-dried. The freeze-drying is performed according to the following steps S41 to S48 to obtain red pigment of red yeast rice, wherein:

[0048] S41. Dehydrate in an environment with a temperature of -25°C and a vacuum degree of 10 Pa for 2 hours;

[0049] S42. Dehydrate in an environment with a temperature of -15°C and a vacuum degree of 10 Pa for 2 hours;

[0050] S43, dehydrate in an environment with a temperature of -6°C and a vacuum degree of 10 Pa for 2 hours;

[0051] S44, dehydrate in an environment with a temperature of 1°C and a vacuum degree of 10 Pa for 2 hours;

[0052] S45. Dehydrate in an environment with a temperature of 6°C and a vacuum degree of 10 Pa for 6 hours;

[0053] S46, dehydrate in an environment with a temperature of 10°C and a vacuum degree of 10 Pa for 1 hour;

[0054] S47, dehydrate in an environment with a temperature of 20°C and a vacuum degree of 10 Pa for 1 hour;

[0055] S48. Dehydrate in an environment with a temperature of 30°C and a vacuum degree of 10 Pa for 8 hours.

[0056] [Example 2]

[0057] A method for preparing red pigment of monascus comprises the following steps:

[0058] S1. Inoculate the Monascus species into a basal culture medium, control the temperature at 35° C., and culture in a shake flask for 6 days; wherein the Monascus species is a purple Monascus species numbered CGMCC No. 3.15548 purchased from the Institute of Microbiology, Chinese Academy of Sciences, and the basal culture medium comprises 10 g of rice flour, 2 g of corn steep liquor powder, 1 g of glucose, 10 g of peptone, 15 g of sodium nitrate, 0.2 g of magnesium sulfate, and 0.15 g of potassium dihydrogen sulfate, and the pH is adjusted to 7.0 to obtain a culture medium;

[0059] S2. After the bacterial colonies in step S1 mature, the solid residue is centrifuged and separated. 4 times the volume of alcohol with a concentration of 95% or more is added. The mixture is stirred at a stirring speed of 100 r / min for 10 h. The liquid is then separated and concentrated at 50° C. using a low-temperature vacuum concentrator to obtain a concentrated solution. The solid content of the concentrated solution is 38.2%;

[0060] S3. Add a protective agent to the concentrated solution of step S2, stir at a high speed of 15000r / min for 3min, and then cool to -45°C for solidification; the protective agent is specifically maltodextrin with a DE value of 16-20, and the amount of maltodextrin is 25% by weight of the concentrated solution of step S2;

[0061] S4. The product solidified by cooling in step S3 is freeze-dried. The freeze-drying is performed according to the following steps S41 to S48 to obtain red pigment of red yeast rice, wherein:

[0062] S41. Dehydrate in an environment with a temperature of -20°C and a vacuum degree of 5 Pa for 1 hour;

[0063] S42, dehydrate in an environment with a temperature of -10°C and a vacuum degree of 5 Pa for 1 hour;

[0064] S43, dehydration in an environment with a temperature of 0°C and a vacuum degree of 5 Pa for 4 hours;

[0065] S44, dehydrate in an environment with a temperature of 5°C and a vacuum degree of 5 Pa for 4 hours;

[0066] S45, dehydrate in an environment with a temperature of 10°C and a vacuum degree of 5 Pa for 4 hours;

[0067] S46. Dehydrate in an environment with a temperature of 15°C and a vacuum degree of 5 Pa for 2 hours;

[0068] S47, dehydrate in an environment with a temperature of 25°C and a vacuum degree of 5 Pa for 2 hours;

[0069] S48. Dehydrate for 6 hours in an environment with a temperature of 35°C and a vacuum degree of 5Pa.

[0070] [Example 3]

[0071] A method for preparing red yeast rice pigment is different from that of Example 1 in that: in S3, a different protective agent is used.

[0072] In this embodiment, the protective agent in step S3 is gum arabic with a molecular weight of 220,000-300,000, and the amount of gum arabic used is 6% of the weight of the concentrated solution in step S2.

[0073] [Example 4]

[0074] A method for preparing red yeast rice pigment is different from that of Example 1 in that: in S3, a different protective agent is used.

[0075] In this embodiment, the protective agent in step S3 is a sodium alginate aqueous solution with a mass concentration of 2%, and the amount of the sodium alginate aqueous solution with a mass concentration of 2% is 0.3% by weight of the concentrated solution in step S2; wherein, the sodium alginate aqueous solution with a mass concentration of 2% is obtained by uniformly mixing sodium alginate with a molecular weight of 70,000-80,000 and water in a weight ratio of 2:98.

[0076] [Example 5]

[0077] A method for preparing red yeast rice pigment is different from that of Example 1 in that: in S3, a different protective agent is used.

[0078] In this embodiment, the protective agent in step S3 includes maltodextrin with a DE value of 16-20, gum arabic with a molecular weight of 220,000-300,000, and a sodium alginate aqueous solution with a mass concentration of 2%, wherein the amount of maltodextrin is 15% of the weight of the concentrate in step S2, the amount of gum arabic is 6% of the weight of the concentrate in step S2, and the amount of the sodium alginate aqueous solution with a mass concentration of 2% is 0.3% of the weight of the concentrate in step S2. In this embodiment, the sodium alginate aqueous solution with a mass concentration of 2% is obtained by uniformly mixing sodium alginate with a molecular weight of 70,000-80,000 and water in a weight ratio of 2:98.

[0079] [Example 6]

[0080] A method for preparing red yeast rice pigment is different from that of Example 1 in that: in S3, a different protective agent is used.

[0081] In this embodiment, the protective agent in step S3 includes maltodextrin with a DE value of 16-20, gum arabic with a molecular weight of 220,000-300,000, and a sodium alginate aqueous solution with a mass concentration of 2%, wherein the amount of maltodextrin is 20% by weight of the concentrate in step S2, the amount of gum arabic is 5% by weight of the concentrate in step S2, and the amount of the sodium alginate aqueous solution with a mass concentration of 2% is 0.25% by weight of the concentrate in step S2. In this embodiment, the sodium alginate aqueous solution with a mass concentration of 2% is obtained by uniformly mixing sodium alginate with a molecular weight of 70,000-80,000 and water in a weight ratio of 2:98.

[0082] [Example 7]

[0083] A method for preparing red yeast rice pigment is different from that of Example 1 in that: in S3, a different protective agent is used.

[0084] In this embodiment, the protective agent in step S3 includes maltodextrin with a DE value of 16-20, gum arabic with a molecular weight of 220,000-300,000, and a sodium alginate aqueous solution with a mass concentration of 2%, wherein the amount of maltodextrin is 25% by weight of the concentrate in step S2, the amount of gum arabic is 4% by weight of the concentrate in step S2, and the amount of the sodium alginate aqueous solution with a mass concentration of 2% is 0.2% by weight of the concentrate in step S2. In this embodiment, the sodium alginate aqueous solution with a mass concentration of 2% is obtained by uniformly mixing sodium alginate with a molecular weight of 70,000-80,000 and water in a weight ratio of 2:98.

[0085] [Example 8]

[0086] A method for preparing red yeast rice pigment, which differs from [Example 6] in that: in this embodiment, the malt paste selection in step S3 uses maltodextrin with a DE value of 4-6.

[0087] [Example 9]

[0088] A method for preparing red yeast rice pigment is disclosed, which differs from Example 6 in that: in this embodiment, guar gum is used instead of gum arabic in step S3.

[0089] [Example 10]

[0090] A method for preparing red pigment of Monascus koji, which differs from Example 6 in that: in this embodiment, a sodium alginate aqueous solution with a mass concentration of 2% is obtained by uniformly mixing sodium alginate with a molecular weight of 140,000-150,000 and water in a weight ratio of 2:98.

[0091] [Example 11]

[0092] A method for preparing red pigment of Monascus koji, which differs from Example 6 in that: in step S4, freeze drying is performed according to the following steps S41 to S48:

[0093] S41. Dehydrate in an environment with a temperature of -25°C and a vacuum degree of 10 Pa for 3 hours;

[0094] S42, dehydrate in an environment with a temperature of -15°C and a vacuum degree of 10 Pa for 3 hours;

[0095] S43, dehydrate in an environment with a temperature of -6°C and a vacuum degree of 10 Pa for 1 hour;

[0096] S44, dehydrate in an environment with a temperature of 1°C and a vacuum degree of 10 Pa for 1 hour;

[0097] S45. Dehydrate in an environment with a temperature of 6°C and a vacuum degree of 10 Pa for 4 hours;

[0098] S46. Dehydrate in an environment with a temperature of 10°C and a vacuum degree of 10 Pa for 3 hours;

[0099] S47, dehydrate in an environment with a temperature of 20°C and a vacuum degree of 10 Pa for 4 hours;

[0100] S48. Dehydrate in an environment with a temperature of 30°C and a vacuum degree of 10 Pa for 5 hours.

[0101] Comparative Example

[0102] [Comparative Example 1]

[0103] A method for preparing red pigment of Monascus koji, which differs from Example 1 in that:

[0104] No protective agent maltodextrin was added in step S3.

[0105] [Comparative Example 2]

[0106] A method for preparing red pigment of Monascus koji, which differs from Example 1 in that:

[0107] In step S3, sodium alginate is used as the protective agent, and sodium alginate is directly added to the concentrated solution of step S2. The amount of sodium alginate used is 0.02% by weight of the concentrated solution of step S2.

[0108] Performance testing

[0109] (1) Yield: Calculate the yield of red yeast rice pigment in each embodiment and comparative example, wherein red yeast rice pigment yield = (red yeast rice pigment freeze-dried powder unit color value * total weight) / (freeze-dried solution unit color value * total weight) * 100%, wherein the unit color value of red yeast rice pigment freeze-dried powder and the unit color value of the solution before freeze-dried are the average value of the color value of three randomly selected samples, and record the standard deviation of the color value of the three red yeast rice pigment freeze-dried powder samples at the same time. The smaller the standard deviation, the better the product uniformity. Wherein, the color value detection is carried out with reference to Appendix A in GB 1886.181-2016 "National Food Safety Standard Food Additive Red Yeast Rice".

[0110] (2) Diffusion time: Accurately weigh 1 g of red yeast rice pigment powder sample, use a 100 mL measuring cylinder of the same specification to measure 100 mL of distilled water, pour the red yeast rice pigment powder from the top of the measuring cylinder, observe the red yeast rice pigment powder, and record the time required for the red color in the measuring cylinder to diffuse to the bottom of the measuring cylinder. The shorter the diffusion time, the faster the dissolution rate of the red yeast rice pigment.

[0111] (3) Loss on drying: Refer to the direct drying method in GB 5009.3-2016 “National Food Safety Standard - Determination of Water in Food” for testing. The lower the loss on drying, the lower the water content of the product.

[0112] (4) Thermal stability: The red pigment of each embodiment and comparative example was dissolved in water to prepare a diluted sample solution with an absorbance of about 1.1, and the specific absorbance A1 of the diluted sample solution corresponding to each embodiment and comparative example was tested. Then, the diluted sample solution prepared in each embodiment and comparative example was poured into a colorimetric tube to prepare 4 sets of parallel samples. Subsequently, each parallel sample was placed on a test tube rack, placed in a water bath at 90°C for 6 hours, taken out, and cooled in a dark place. The average absorbance of the 4 parallel samples after cooling was tested and recorded as A2. Among them, the smaller the difference between A1 and A2, the better the thermal stability of the red pigment sample.

[0113] Table 1 Yield and color value standard deviation record

[0114]

[0115]

[0116] Table 2 Diffusion time and drying loss record

[0117] sample Diffusion time / s Loss on drying / % Example 1 60 4.85 Example 2 60 4.46 Example 3 60 4.26 Example 4 60 4.91 Example 5 40 2.51 Example 6 40 2.12 Example 7 40 2.46 Example 8 60 3.67 Example 9 60 3.48 Example 10 60 3.75 Example 11 40 2.78 Comparative Example 1 60 2.08 Comparative Example 2 90 6.92

[0118] Table 3

[0119]

[0120]

[0121] Combining the test data in Comparative Example 1 and Example 1 and Tables 1-3, it can be seen that in Comparative Example 1, no protective agent was added, and the yield of the red pigment obtained by the freeze-drying method was less than 95%. At the same time, the thermal stability of the red pigment was significantly reduced.

[0122] Combining Comparative Example 2 with Example 2 and the test data in Tables 1-3, it can be seen that the sodium alginate in Comparative Example 2 was not added in the form of an aqueous solution, and the yield of the resulting red pigment of Monascus was less than 95%. In addition, there were disadvantages such as poor product uniformity, slow dissolution rate, low drying efficiency, and poor thermal stability. Therefore, sodium alginate should be added in the form of an aqueous sodium alginate solution.

[0123] Combined with the test data in Example 1, Examples 3-7 and Tables 1-3, it can be seen that when maltodextrin, gum arabic and sodium alginate are combined as protective agents, the wall material structure on the surface of the red yeast rice pigment can be improved under the synergistic cooperation of maltodextrin, gum arabic and sodium alginate in a reasonable ratio. The wall material structure can not only be protected from ice crystal damage and denaturation and degradation during the freeze-drying process, but also has a uniform and fine porous structure, which facilitates the diffusion and sublimation of water while preventing the loss of effective ingredients, thereby improving the drying effect of the red yeast rice pigment and, at the same time, improving the thermal stability of the red yeast rice pigment.

[0124] Combining Example 6 and Example 8 and the test data in Table 1-3, it can be seen that the maltodextrin preferably has a DE value of 16-20. The maltodextrin within this DE value range has a shorter molecular chain, a lower degree of polymerization, and good solubility and dispersibility, which can improve the drying effect and product uniformity of the red yeast rice pigment while improving the water solubility rate and quality stability of the red yeast rice pigment.

[0125] Combining the test data in Example 6 and Example 9 and Table 1-3, it can be seen that when guar gum is used instead of gum arabic, the drying effect, product uniformity, water solubility rate and thermal stability of Monascus red pigment are all reduced, indicating that maltodextrin, gum arabic and sodium alginate can synergistically improve the drying effect, product uniformity, water solubility rate and thermal stability of Monascus red.

[0126] Combining Example 6 and Example 10 and the test data in Table 1-3, it can be seen that in a sodium alginate aqueous solution with a mass concentration of 2%, the molecular weight of sodium alginate is preferably in the range of 50,000-100,000, which is beneficial to improving the drying effect and product uniformity of the red yeast rice pigment, and is beneficial to obtaining a red yeast rice pigment with fast water solubility and stable quality.

[0127] The dehydration time of the red yeast rice pigment at different temperatures in Example 11 is different from that in Example 6, but the total dehydration time remains the same. Combined with the test data in Tables 1-3, it can be seen that freeze-drying the red yeast rice pigment using the freeze-drying step claimed in this application is more conducive to improving the product uniformity, drying efficiency and thermal stability of the red yeast rice pigment.

[0128] This specific implementation manner is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the specific implementation manner as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing red pigment of Monascus koji, characterized in that: The following steps are involved: S1. Inoculate the Monascus species into the basic culture medium to carry out batch expansion operations; S2. After the bacterial colonies in step S1 mature, centrifuge to obtain the solid residue, add 3-5 times the volume of 95% or higher alcohol, stir, then separate the solid and liquid to obtain the liquid, and concentrate at 45°C-55°C to obtain a concentrated solution; S3. Add a protective agent to the concentrated solution of step S2, stir at high speed until uniform, and cool and solidify, wherein the protective agent is at least one of maltodextrin, gum arabic, and sodium alginate aqueous solution; S4, freeze-drying the product after cooling and solidification in step S3 to obtain red pigment of Monascus; The protective agent includes maltodextrin, gum arabic and a sodium alginate aqueous solution with a mass concentration of 1.5%-2.5%, wherein the amount of maltodextrin is 15%-25% by weight of the concentrated solution in step S2, the amount of gum arabic is 4%-6% by weight of the concentrated solution in step S2, and the amount of the sodium alginate aqueous solution with a mass concentration of 1.5%-2.5% is 0.2%-0.3% by weight of the concentrated solution in step S2; The DE value of the maltodextrin is 16-20; the molecular weight of the gum arabic is 220,000-300,000; In step S3, the curing temperature is (-38°C) to (-45°C).

2. The method for preparing a red yeast rice pigment according to claim 1, wherein: The amount of maltodextrin used is 20% by weight of the concentrated solution in step S2, the amount of gum arabic used is 5% by weight of the concentrated solution in step S2, and the amount of sodium alginate aqueous solution with a mass concentration of 1.5%-2.5% used is 0.25% by weight of the concentrated solution in step S2.

3. The method for preparing a red yeast rice pigment according to any one of claims 1 to 2, wherein: In the sodium alginate aqueous solution with a mass concentration of 1.5%-2.5%, the molecular weight of sodium alginate is 50,000-100,000.

4. The method for preparing a red yeast rice pigment according to any one of claims 1 to 2, wherein: In step S3, the rotation speed of the high-speed stirring is 10000 r / min-15000 r / min.

5. The method for preparing a red yeast rice pigment according to any one of claims 1 to 2, wherein: In step S4, the freeze-drying comprises the following steps: S41. Dehydrate for 1-2 hours in an environment with a temperature of -25°C to -20°C and a vacuum degree of 5Pa-10Pa; S42. Dehydrate for 1-2 hours in an environment with a temperature of -15°C to -10°C and a vacuum degree of 5Pa-10Pa; S43. Dehydrate in an environment with a temperature of -6°C to 0°C and a vacuum degree of 5Pa-10Pa for 2-4 hours; S44. Dehydrate in an environment with a temperature of 1°C to 5°C and a vacuum degree of 5Pa-10Pa for 2-4 hours; S45. Dehydrate for 4-6 hours in an environment with a temperature of 6°C to 10°C and a vacuum degree of 5Pa-10Pa; S46. Dehydrate for 1-2 hours in an environment with a temperature of 10°C to 15°C and a vacuum degree of 5Pa-10Pa; S47. Dehydrate for 1-2 hours in an environment with a temperature of 20°C to 25°C and a vacuum degree of 5Pa-10Pa; S48. Dehydrate for 6-8 hours in an environment with a temperature of 30℃~35℃ and a vacuum degree of 5Pa-10Pa.

6. A red yeast rice pigment, characterized in that: The invention is prepared by the method for preparing the monascus red pigment according to any one of claims 1 to 5.

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